This invention pertains to devices for measuring displacement, and, in particular, to an improved peak strain detection linear displacement sensor system for smart structures for use in situations that call for micro miniature, high resolution passive peak strain detector for determining damage or movement in structures such as buildings, bridges, aircraft frames, landing gear and composite structures.
There have been a number of attempts to develop highly accurate miniaturized sensors to be used by industry to measure displacement, elongation, and strain. Examples of these type of devices include U.S. Pat. No. 4,813,435 issued to Steven W. Arms on Mar. 21, 1989, based on Hall Effect sensors. An attempt to create a strain sensor capable of detecting peak strains is the U.S. Pat. No. 5,086,651 for a transformation induced plasticity (TRIP) steel device which shows units that have a simplicity of design and construction. However, TRIP units have limitations that include its large size, inherent nonlinearity, low resolution and irreversible response due to yielding.
Critical civilian and military structures require smart sensors in order to report their strain histories in order to insure safe operation after being subjected to exposure from potentially damaging load from hurricanes, earthquakes or military action or prolonged exposure to the elements.
It is the object of this invention to teach a micro miniature, high resolution, linear displacement sensor for peak strain detection in smart structures which avoids the disadvantages of and limitations of previous systems, and addresses the needs of linear position sensing in a critical structural situations. What is needed is a system which provides a high resolution, linear, peak displacement or strain measurement with very small sensors (approximately 1.5 mm diameter), without requiring power to hold its measurement, and, that is capable of being re-used.
It is the object of this invention to teach a peak strain detection linear displacement sensor system for smart structures, for use in the measurement of the linear displacement or strain of a structure using a micro miniature, high resolution, passive peak strain detector for determining damage or movement in the structure being monitored such as buildings, bridges, aircraft frames, landing gear, composite structures or the like, comprising a peak strain detection unit for measuring the deflection found in at least one structure being measured; said peak strain detector unit having means for positioning said peak strain detection unit and holding said peak strain detection unit in said position; said positioning and holding means comprises first means for clamping said peak strain detection unit, and second means for compressing or extending said peak strain detection unit; said positioning and holding means having attaching means for locating said peak strain linear displacement sensor system for smart structures on the structure or structures to be measured; means for restricting said peak strain detection unit to hold peak deflection of said peak strain detection unit; and means for measuring the levels of strain on said peak strain detection linear displacement system. Also, it is the object of this invention to teach a peak strain detection linear displacement sensor system for smart structures, for use in the measurement of linear displacement or strain of a structure using a micro miniature, high resolution, passive peak strain detector for determining damage or movement in the structure being monitored such as buildings, bridges, aircraft frames, landing gear, composite structures or the like, comprising in combination a peak strain detection unit for measuring the deflection found in at least one structure being measured, the peak strain detection unit having a slideable core, positioning means for placing said peak strain detection unit in a predetermined position, means for attaching said peak strain detection unit to said structure being measured, restriction means for permitting of said slideable core at the point of maximum deflection, and measurement means for determining the level of deflection on the peak strain detection unit.